DSH 725 Abnormal operation

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DSH 725

Abnormal operation 5 Q3 s& C- e  ]1 |1 ?9 e; @

19.102 $ N( `- f, ^# h. `9 o5 n: E

60335-2-6(ed.5)

+ }# Z, P1 R+ D  d/ n3 y7 X' LQuestion:
In 19.102 of IEC 60335-2-6:2002, it is required to short-circuit the thermal control for the test. Note 5 of Sub-clause 19.1 of IEC60335-1:2006 explains that instead of short-circuiting, controls may be render inoperative.
7 @" h5 U; M2 J8 k1 r9 T( nIn induction hobs, the thermal control of hob elements is normally a NTC controlled by the micro-controller. Short-circuit or open circuit of the NTC is easily detected by the microcontroller, but fixing the NTC in an intermediate value may not be detected.
IEC60730-1:2007, Annex J has the requirements for thermistors. There is a test for the drift of the R/T characteristic when the control is classified as Type 2.
, p) p( M% Q; ?3 W/ K4 v' o2 cShould the NTC be fixed at a specific value so as to render the thermal control inoperative, which is the condition required to be checked by 19.102?
" [) E8 U/ o! D% lDecision:
) R/ d0 _+ Y+ uThe NTC can be fixed to a specific value. This value must be in the middle of the operating range of the NTC, so as to avoid hysteresis problems that may happen towards the end of the range.

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